Consider the titration of 50.0 mL of 0.0500 M H2NNH2 (a weak base; Kb = 1.30e-06) with 0.100 M HClO4. Calculate the pH after the following volumes of titrant have been added: (a) 0.0 mL pH = (b) 6.3 mL pH = (c) 12.5 mL pH = (d) 18.8 mL pH = (e) 25.0 mL pH = (f) 37.5 mL pH =